Update create_foreign_table.sgml

Author: ChenHuajun

postgresql/doc/src/sgml/ref/create_foreign_table.sgml

@@ -95,7 +95,7 @@ CREATE FOREIGN TABLE [ IF NOT EXISTS ] <replaceable class="parameter">table_name
 { NOT NULL |
   NULL |
   CHECK ( <replaceable class="parameter">expression</replaceable> ) [ NO INHERIT ] |
-  DEFAULT <replaceable>default_expr</replaceable> }
+  DEFAULT <replaceable>default_expr</replaceable> |
   GENERATED ALWAYS AS ( <replaceable>generation_expr</replaceable> ) STORED }
 
 <phrase>而 <replaceable class="parameter">table_constraint</replaceable> 是：</phrase>